[Hps] ECal position

[Gabriel CHARLES]

Hum... but as Stepan said, this difference was not present during the 
run in December. So the ECal is probably centered. I don't remember the 
beam being positionned to have the same rate in the top and bottom ECal.

Regards,
  Gabriel

Le 2015-05-06 19:12, Gabriel CHARLES a écrit :
> That's right!
> 
>    When we installed the ECal the first time, the distance between top
> ECal and vacuum chamber, and bottom ECal and vacuum chamber were very
> similar (we moved the calorimeter mm by mm so we could see a 1 mm
> difference), we concluded that it was due to the position of the
> chamber. There may be 1 mm difference between the center of the chamber
> and the "true" center, so it was hard to conclude at that time. The
> calorimeter box could also be 1 mm down, the targets used for the 
> survey
> being independant of the box.
> 
>   Anyway, your idea is probably right, could tracking help?
> 
> Regards,
>   Gabriel
> 
> Le 2015-05-06 18:36, Nelson, Timothy Knight a écrit :
>> Here are the results of the ECal survey shown in January.  Am I wrong
>> that this indicates that the bottom ECal is closer to the beam by 1 -
>> 2 mm (and about 1.5 mm in the middle where rates are high) compared to
>> the top?  If so, then that could explain the rate effects we see in
>> the top vs. bottom ECal, since that’s about 1 mr change in acceptance.
>> 
>> Tim
>> 
>> 
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-- 
Gabriel CHARLES
Institut de Physique Nucléaire d'Orsay